Method of manufacturing ductile high aluminum iron alloy



May 12, 1959 IOSAMU MADONO 2,886,428 METHOD OF MANUFACTURING DUCTILE HIGH ALUMINUM IRON ALLOY Filed April 1. 1957 IIIIII INVENTORQ ttes atet 2,886,428 Patented May 12, .1959

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United METHOD OF MANUFACTURING DUCTILE HIGH ALUMINUM IRON ALLOY Osamu Madono, Kumagaya-City, Japan I Application April 1, 1957, Serial No. 649,667 "Claims priority, application Japan December 26, 1956 Claims. (Cl. 75-12) The present invention relates to a method of manufacturing ductile high aluminum-iron alloys by means of a consumable electrode type arc furnace, having an advantage of the freedom of selection of the starting materials, which permits carbon or alloy steel to be more effectively used than electrolytic or ingot iron. In spite of the freedom of the selection of the starting materials, the products, compared with the existing high aluminumiron alloys made by other methods, are more ductile, and yet have high strength, heat resistance, oxidation resistance, together with excellent magnetic properties and high electrical resistance.

It has been well-known for many years that aluminum greatly improves the above various properties of ferrous alloys. But their use is limited because of the difliculty of producing the inherently brittle aluminum ferrous alloys in usable form. That is, ferrous alloys with an aluminum content less than about 5% may be either hot or cold worked without difiiculty; ferrous alloys containing aluminum in an amount more than about 5% becomes too .brittle for cold working. The ductility of the aluminum ferrous alloys is strongly influenced by the presence of extremely small amounts of carbon, which causes embrittlement because of deposition of carbide at the grain boundaries; On the other hand, carbon-free aluminum ferrous alloys are apt to become embrittled by the'contamination of alumina inclusions. Therefore, the basic requirement for a high-quality aluminum ferrous alloy is freedom from alumina inclusions as well as less carbon content to such a degree as can be technically attained. 3311 preparing experimental aluminum ferrous alloys, electrolytic iron may be used to meet this requirement, 'but such iron is too expensive for the production on a com mercial scale.

At molten iron temperatures, aluminum is a powerful cleoxidizer. This characteristic must be considered when it is used as an alloying element, because an undesirable quantity of alumina inclusions will be present unless precautions are taken. It is due to this fact that special techniques such as vacuum or inert gas melting have conventionally been recommended as the best way to obtain satisfactory results, though they have various disadvantages such as difficulty in operation, necessity of special refractories, etc.

, As has already been mentioned, in manufacturing the aluminum ferrous alloys by the method of the present invention, carbon or alloy steel can preferably be used as the starting material in the form of thin elongated members, such as rods having a small diameter, strips or-tubes with thin-wall thickness. When the aluminum ferrous alloys are required to contain no special elements other than aluminum, rods of pure metal may likewise be used for their addition. However, all these materials above mentioned not only contain more or less amount of 1 carbon but also there are always present oxides on their surfaces. Precautions must, therefore, be taken to insure that the oxides will completely be reduced, and further that the carbon will be removed as completely as possible.

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I have found that a heat-treatment of steel in the form of thin elongated members, such as rods, strips or tubes at temperatures above 700 C., in an atmosphere of hydrogen, is a simple and yet effective method of reducing both the carbon content and oxides to a maximum. In the existing methods, molten iron has to be given a decarburizing and deoxidizing treatment with hydrogen, followed by vacuum treatment. Compared with the method of the present invention, the molten methods should be equally effective; but hydrogen is potentially explosive, especially at'those elevated temperatures, so that its practical use is limited. By contrast, the solid method is both simple and economical, and yet the carbon content can easily be reduced to a sufficiently low level to obtain ductile aluminum ferrous alloys. Thus, I am, as far as I know, the first to adopt the solid method as a standard procedure prior to alloying iron with aluminum.

To illustrate the method according to the present invention, reference is made to the accompanying drawing in which:

Fig. 1A is a side elevation, partly in section of a batch type furnace with a plurality of steel rods packed therein, the view being taken along line X--X of Fig. 1B;

Fig. 1B is a section along in YY of Fig. 1A;

Fig. 2 is a cross sectional view of anelectrode prepared according to the present invention;

Fig. 3A is a sectional view of an apparatus for preparing an electrode according to the method of the present invention;

Fig. 3B is a section through line B-B of Fig. 3A;

Fig. 4 is a sectional view of a modified form of an electrode prepared according to the present invention; and

Fig. 5 is a schematic representation of a consumable electrode electric arc furnace having a water cooled crucible.

To insure the decarburization of those thin, elongated members, a batch type or a tumbling furnace may be used. The batch type furnace consists of a long horizontal heating chamber, in which are arranged a number of tubes made of stainless steel. The arrangement for decarburizing is schematically shownin Fig. 1, which illustrates one of stainless steel tubes to be arranged in the long horizontal heating chamber of a batch type furnace. The steel rods 1 are compactly loaded in lengthwise parallel relationship within the tube 2, through which hydrogen is caused to flow from inlet 3 to outlet 4. In this case, the time needed for complete decarburization depends upon the carbon content, the diameter of rods, temperature and the composition of the atmosphere. As is well-known, moist hydrogen is preferred to dry hydrogen for its decarburizing ability. On the other hand, the tumbling furnace has an advantage which brings a good contact of hydrogen with the rods, resulting in uniform and complete decarburization. It is, however, unsuitable for long rods with excessively small diameter to be treated in such a tumbling furnace, because they are liable to 'get entangled.

The next step is to prepare a consumable electrode such as are shown in Fig. 2, 3 and 4. T o prepare the electrode shown in Fig. 2, the decarburized iron rods 5 are bundled together to makean electrode with a material, the essential constituent of which is aluminum. For example, there may be used substantially pure or alloy aluminum in the form of rods 6 with a small diameter. Then the bundle is forced into a closely fitting iron tube 7 which has equally been decarburized. The tube thus filled up may be usable for a consumable electrode. In this connection, the sealing of the bundle by an iron tube is effective to prevent the ferrous rods from reoxidation, particularly when melting is carried out in the air. Further, it is worth mentioning that a uniform distribu- 700? In thisgconnetcft'ion, I ha prep rin t l no r i ..con ce ed, i'sfactcry of the'furnace isfvery simple, and .it'is possible to cast a 3 tion of aluminum containing rods in the structure of the electrode 'iethe'indispens'aelemeans to insure a homogeneity of the resulting alui'rjlinum ferrous alloys.

Fig. 3 is .a vi e w. qfanothertype of consumab le electrode consisting ofir'onjrodsI packedfingaluniinunfi To prepare ltype iei cubaelmoiten" aluiriinum,'8 contained in a n 1 el gjpotfliofthe apparatus of Fig; 3a ,isisucked into the; :on tube '9 by, means of avacuum ,so as to "fill up aroundthe iron rods 10 shown iir-thelcrossj sectional .view of Fig; 3b. The method is efiectiveespecially,when alloy aluminum is to be alloyedwith' iron, because high alloy is too brittletobe drawntoa fine rod.

In. both methods .above mentioned, the". operations are carried .outin' two parts; steel rods larel'ffirst,iheat-treated in an atmosphere of hydrogen, and .then ombined with aluminum to prepare thelfectrodeQ Thrs is dueto the Tfact that; sinceLaluminurn .ni1ts. ,at"6'55." C, it .cannot be heat treated together w th, steeli'dd raturesiabove ound' 'amuiqe of electrode .by us ng ,efiectively steel-clad rods'in pace of al umiiium rods. The clad rods are. made bydrawiugn steel tubelcontainin'g j ue e' o l minum. Thenc'a ibelhated1atl mperatures above700' C. without becoming brittle .Ormelting though precautions must betaken. lest thetemp'erature should'be elevated .above;8'5.0 ,IC. i

is shownin' Fig. 4,: theclad rods .l t arebundled together with. steel rods. 15 and s'tufiedinto a steel tube 16. Then the steel tube is heatl-t'reatedin an atmosphere of hydrogen in accordance with itheflp'rocedure already mentioned. After completing decarburizingtheiron tube containing the enemas. may .imm'ediatelybe used for a consumable electrode. 'The electrode thus prepared is free from trouble caused by reoxidation of iron rods as welllasthe difficulty in removal of alumina film existing on the surface of an aluminum. Therefore, the advantages of this type. electrode be noted as follows: 1. Improved chemicalfhomogeneitw 2.-,Less contamination from alumina inclusions. 3. General simplification and improvement in preparingthe. consumable electrode.

Lastly, the thirdstep'is to. melt'the consumableelee trode by'an electric arc in a water-cooled metal crucible. Fig. shows 'thefp'rocedure schematically. As can be seen: from this illustration, .the consumable electrode 17 is to be melted by electric-arc. 18 in .a water-cooled crucible19. Though this furnace for'casting high aluminumiron alloys is substantially'similar to. those which are generally used for-titanium orgzir'conium, in'the furnace employed by the present ,inyentionlneither vacuum. nor inert atmosphere is absolutely needed. I have found that, at' ljeast so f ar'as the'ductility'andioxidationresistance are 7 melting injair' is .goodfe'nbugh to obtain a satresulting product.,l Therefore, theconstruction continuous ingot 20,byiusing',a retractable bottom 21.

Further, 'theinvention is illustrated ,by the following examples in which, the compositionsfot the starting materials used were as followsz" i (1). Steel rod 2 :mm. in1diameter;i0.25% C, 0.42% Mn,

(2) Steel tube 2 mm. in wall! thickness; 0.16% 0,1035% -Mn, 0.03% P,'-0.03% S.

(3) Stainless steel rod 3 mm. ,inzdiameter; ;l8.5'%..-Cr,

(4) ..Aluminum rod2 mm. in diameter; 99.7 Al.

Example .1 p The steel rods andtubeswereheated at 750 C. in an drawn to 1 mm. in diameter had a tensile strength of 62 kg./mm'. and the elongation was 35% on measuring on 20 mm. gauge length.

Example 2 The steel rods and tubes were heated at 800 C. in an atmosphere of hydrogen for 24 hours. The resulting alloy containing 14% a1uminum, co uld.be cold,ro1led.to 1 mm. thickness sheet and drawn-to Lmm. diameter wire.

I Example 3 The steel rods and tubes were '--hydrog cntreatcd at 800 C. for 20 hours. After the decarburizationwas completed, molten alumnium-alloy containing 15%"silicon was sucked into the iron tube bymeans of the vacuum method to fill-up around the rods. Theresulting'alloy contained 13%-aluminum and 2% "silicomlt could-easlly be cold rolled to 1 mm. thicknesssheet.

Examplefi The diameter of clad rods used-was '4'mm., that of aluminum cores being 2mm. 26 pieces of the cladrod were stufied into a closely fitting tube 32 mm. in inner diameter and 1 mm. in wallthickness. The tube was treated by hydrogen at 750 C. for 15 hours. The resu1ting alloy contained 7.6% aluminum, and was ductile enough to be cold drawn to;0.2 mm. thickness with ease.

The descriptions are intended to be illustrative only and it is to be understood that changes and variationsmay be made withoutdeparting from the spirit andscope of the invention as defined by the appended claims.

I claim:

1. A method of manufacturing ductilehigh aluminum ferrous alloys containing up to 18% aluminum, comprising the steps of heating a ferrous alloy while it is in a solid state toa temperature in excess of 700C. in an atmosphere of hydrogen fordecarburizing saidferrous carburized ferrousalloy and a material :consistingessentially of aluminum, and using the thus preparedelectrodc as an electrodein an electrode typearc furnace to cast an ingot in a watercooled metallic crucible.

2. A method of manufacturing ductile high aluminum ferrous alloys containing up to 18% aluminum, "comprising the steps of preparing anelectrode'by combining ingthe thus decarburized elongated members together with elongated aluminum containing rods into a tube "of decarburized ferrous materiaLand using the thus prepared electrode as an electrode in an electrode type are furnace to cast an ingot in a water cooled metallic crucible.

4. A method of manufacturing ductile high aluminum ferrousalloys containing up to 18% aluminum-commie ing the steps of forming an electrode by inserting a 'plualloy, preparing an electrodeby combining the thus dea rality of thin walled steel tubes having an inner core of aluminum and a plurality of slender steel rods into a thin walled steel tube, heating the thus formed electrode to a temperature of from 700 to 850 C. in an atmosphere of hydrogen to decarburize said electrode, and using the thus decarburized electrode as an electrode in an electrode type are furnace to cast an ingot in a water cooled metallic crucible.

5. A method of manufacturing ductile high aluminum ferrous alloys containing up to 18% aluminum, comprising the step of heating a plurality of thin elongated steel members to a temperature of from 700 to 850 C. in an atmosphere of hydrogen, preparing an electrode by 6 placing the thus decarburized members in a thin walled tube of decarburized ferrous material, placing molten aluminum containing material in said tube around the thin elongated members therein, and using the thus prepared electrode as an electrode in an electrode type are furnace to cast an ingot in a water cooled metallic crucible.

References Cited in the file of this patent UNITED STATES PATENTS Boothby et al Mar. 10, 1953 

1. A METHOD OF MANUFACTURING DUCTILE HIGH ALUMINUM FERROUS ALLOYS CONTAINING UP TO 18% ALUMINUM, COMPRISING THE STEPS OF HEATING A FERROUS ALLOY WHILE IT IS IN A SOLID STATE TO A TEMPERATURE IN EXCESS OF 700*C. IN AN ATMOSPHERE OF HYDROGEN FOR DECARBURIZING SAID FERROUS ALLOY, PREPARING AN ELECTRODE BY COMBINING THE THUS DECARBURIZED FERROUS, ALLOY AND A MATERIAL CONSISTING ESSENTIALLY OF ALUMINUM, AND USING THE THUS PREPARED ELECTRODE 